Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$63.53	13.676%	$72.2184	$72.22	$72.20	$72.20
Purchase #2	$204.99	9.205%	$223.8593	$223.86	$223.85	$223.90
Purchase #3	$33.73	11.102%	$37.4747	$37.47	$37.45	$37.50
Purchase #4	$170.90	10.723%	$189.2256	$189.23	$189.25	$189.20
Purchase #5	$11.82	3.325%	$12.213	$12.21	$12.20	$12.20
Purchase #6	$238.89	10.733%	$264.5301	$264.53	$264.55	$264.50
Purchase #7	$66.66	4.264%	$69.5024	$69.50	$69.50	$69.50
7 purchase totals =	$790.52		$869.0235	$869.02	$869.00	$869.00